1.activity_car 佈局

<com.bwei.shoppingcar.AddSubLayout
android:layout_width=“match_parent”
android:layout_height=“match_parent”>

</com.bwei.shoppingcar.AddSubLayout>

2.AddSubLayout

public class AddSubLayout extends LinearLayout implements View.OnClickListener {

private Button mAddBtn;
private Button  mSubBtn;
private TextView mTextNum;

public AddSubLayout(Context context) {
    super(context);
    initView();
}

public AddSubLayout(Context context, @Nullable AttributeSet attrs) {
    super(context, attrs);
    initView();
}

public AddSubLayout(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    initView();
}

private void initView() {
    View view=View.inflate(getContext(),R.layout.car_add_layout,this);
    mAddBtn = view.findViewById(R.id.btn_add);
    mSubBtn = view.findViewById(R.id.btn_sub);
    mTextNum = view.findViewById(R.id.text_number);
    mAddBtn.setOnClickListener(this);
    mSubBtn.setOnClickListener(this);
}

@Override
public void onClick(View v) {
    int number=Integer.parseInt(mTextNum.getText().toString());
    switch (v.getId()){
        case R.id.btn_add:
            number++;
            mTextNum.setText(number+"");
            break;
        case R.id.btn_sub:
            if (number==0){
                Toast.makeText(getContext(),"數量不能小於0",Toast.LENGTH_LONG).show();
                return;
            }
            number--;
            mTextNum.setText(number+"");
            break;

    }
}
 

}
3.car_add_layout 佈局

   android:id="@+id/btn_add"
    android:layout_width="50dp"
    android:layout_height="50dp"
    android:background="@drawable/car_background"
    android:text="+" />

<TextView
    android:id="@+id/text_number"
    android:layout_width="50dp"
    android:layout_height="50dp"
    android:text="1"
   />

<Button
    android:id="@+id/btn_sub"
    android:layout_width="50dp"
    android:layout_height="50dp"
    android:background="@drawable/car_background"
    android:text="-" />